A conventional surface treatment of a fishhook for fishing or the like has been nickel-plating or gold-plating of the surface of a fishhook material, or coating of the surface of the plating layer with an acrylic resin, a urethane resin or the like for enhancement in corrosion resistance.
Furthermore, there has also been proposed formation of a plating layer onto the surface of a fishhook material, the plating layer being combined with a fluororesin of a fine molecular structure on a nickel-phosphorus alloy base material by an electroless treatment (Patent Document 1).
Such a conventional surface treatment, however, has been unable to be conducted while sharpness of a hook tip being kept, and has not been sufficient as a surface treatment of a fishhook for fishing.
In addition, a conventional fishhook coated with Teflon (registered trademark) by plating has been low in impact resistance, and has also been problematic in terms of peeling or lacking of Teflon (registered trademark) plating when subjected to impact with a stone or the like.
On the other hand, as a method for forming a thin film by treating a substrate surface, a method is known where a solution obtained by treating a metallic surfactant having at least one or more hydrolyzable groups with a metal oxide and/or a partial hydrolysis product of a metal alkoxide, and water, in an organic solvent is brought into contact with a substrate surface (Patent Documents 2 and 3, and the like). In addition, other fluorine-based surface treating agent, thiol, sulfide, disulfide or the like is also known as a surface treating agent of a substrate, but any application example thereof to a fishhook or an article similar thereto is not found. Patent Document 3 exemplifies an application of a chemical adsorption film, and exemplifies, as a needle, an acupuncture needle, a sewing needle, a sewing-machine needle, a tatami mat needle, an injection needle, a needle for surgery, a safety pin, or the like, but all of such needles are completely different from a fishhook for fishing or the like for use in water.